Ipswich Digestive Health Group

What is a colonoscopy?

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What is a Colonoscopy?

Colonoscopy is a procedure which enables the doctor to see inside your large bowel. Unlike a barium enema, which takes x-ray photographs, a colonoscopy lets the doctor see the surface inside the bowel directly and provides more detail and accuracy than x-rays. The procedure is performed following extensive preparation of your bowel.


The instrument used is a thin flexible tube containing a video camera. If necessary, small tissue samples biopsies can be taken during the examination, painlessly, for laboratory analysis. Polyps, wart-like growths that can evolve into bowel cancers, can also be removed using a snare wire. Simple food dyes are sometimes sprayed on the bowel to detect early polyps.

How accurate is a Colonoscopy?

Colonoscopy is an important tool for the diagnosis and treatment of many diseases of the large bowel. Colonoscopy is an accurate, although not perfect test. Rarely small early malignancies can be missed. The risk of this is minimised by performing a full colonoscopy to the caecum or terminal ileum, and having a well prepared bowel. The current literature suggests approximately 1-3% of cancers are missed. The chance of developing a bowel cancer in the screening interval after a satisfactory colonoscopy is estimated at about 1 in 2000. This risk is composed of missed lesions, aggressive, rapidly growing lesions, and incompletely resected lesions. The following will help ensure the risk is minimized:

  • 1. Your bowel is very well cleaned.

    It is important you take the bowel preparation correctly.

  • 2. A full colonoscopy to the terminal ileum is performed.

    This is possible in about 98% of patients.

  • 3. The use of Indigo Carmine Dye.

    This is sprayed in the bowel and probably improves the detection of flat polyps. Currently this is relatively new technique but in now used in most patients. Indigo Carmine is a harmless food dye.